1. Field of the Invention
The present invention relates to image forming apparatuses such as copying machines, printers, and facsimiles, and more particularly, to an image forming apparatus, which reuses (reclaims) toner recovered by a cleaner in image forming.
2. Description of the Related Art
As conventional image forming apparatuses, the following image forming apparatus has been widely used. The image forming apparatus is configured such that an electrostatic latent image is formed by exposing a uniformly charged surface of a photoconductor drum, the formed electrostatic latent image is developed and visualized with toner by a developing device, the developed image is transferred onto a sheet of paper, and a residual toner remaining on the photoconductor drum after the transfer is recovered by a cleaner.
In recent years, there have been demands for global environment conservation, and a reduction in the absolute amount of waste discharged from image forming apparatuses has been required. Thus, a recovered toner recycling method has been considered. According to this method, toner recovered by a cleaner after transfer is returned to a developing device and reused (reclaimed) therein.
Meanwhile, in addition to the above-described residual toner, foreign matters (for example, paper debris, etc. created from sheets of paper) reversely transferred onto the photoconductor drum from sheets of paper during transfer may be mixed into the recovered toner. Therefore, when the above-described recovered toner recycling method is employed, the foreign matters also may be carried into the developing device along with the recovered toner. If foreign matters are mixed into the toner within the developing device, the foreign matters and the toner form aggregates and the formed aggregates are moved to the photoconductor drum by developing operation. At this time, if the foreign matters have a charged polarity reverse to that of, for example, the toner, the aggregates, i.e., the foreign matters with the toner may be moved to a non-image portion of the photoconductor drum to cause spotted contamination. Therefore, image quality may deteriorate.
Further, in an image forming apparatus, which uses as a cleaner a cleaning member such as a blade member, coming into pressure contact with the photoconductor drum, a photosensitive layer formed on the photoconductor drum wears away with its use for an extended period of time. Then, if the wear of the photosensitive layer proceeds to some degrees, the charging performance of the photoconductor drum may deteriorate. As a result, image defects may occur such that fogging is caused due to transfer of the toner to the non-image portion.
Accordingly, a technique of suppressing wear of the photoconductor drum has been proposed (see JP 2001-312132 A (pages 5–8)). In this technique, a lubricant composed of metal stearate is contained in a developer, and the lubricant is supplied to the photoconductor drum to form a film composed of metal stearate on the surface of the photoconductor drum.
However, the lubricant supplied to the photoconductor drum does not become the film of the surface of the photoconductor drum in its entirety, but its large portion is removed by the cleaner. At this time, a portion of the lubricant is subjected to a stress. As a result the portion of the lubricant is aggregated and greatly enlarged at a pressure-contact portion between the photoconductor drum and the blade member. Therefore, when the above-described recovered toner recycling method is employed, the greatly enlarged toner along with the recovered toner may also be carried into the developing device. When the greatly enlarged lubricant is mixed into the toner within the developing device, similar to the above-described foreign matters such as paper debris, the greatly enlarged lubricant forms aggregates along with the toner, and the formed aggregates are moved to the photoconductor drum by developing operation. At this time, if the lubricant has a charged polarity reverse to that of, for example, the toner, the aggregates, i.e., the greatly enlarged lubricant with the toner may be moved to a non-image portion of the photoconductor drum to cause spotted contamination. Therefore, image quality may deteriorate.
Accordingly, a technique of removing foreign matters of a predetermined size or more has been proposed (for example see JP Sho.62-144191 (A pages 2–3 and FIG. 2)). In this technique, a mesh filter is provided on a path along which recovered toner is carried from the cleaner to the developing device. Further, another document discloses that a brush roller to which a predetermined bias is applied is provided on a path along which recovered toner is carried from the cleaner to the developing device and that talc carried along with the recovered toner is collected (see JP Hei.5-313543 A (pages 2–3 and FIG. 2)). Moreover, still another document discloses a technique of removing paper debris carried on a photoconductor drum after transfer along with waste toner (see JP Hei.6-282201 A (pages 3–5 and FIGS. 3–4)). In this technique, a brush member to which a predetermined bias is applied is located on downstream of a transfer position of an image to a sheet of paper and on upstream of a cleaning position by a cleaner so as to contact the photoconductor drum.